This invention pertains to motors used down hole in well drilling operations. More particularly it is related to run time totalisers that indicate the amount of time a motor has been actually rotating.
Mud powered motors are used extensively in the well drilling industry, usually to drive drill heads. They are often leased on the basis of rotating hours. When the motor is down hole on a drill string, it may be idle while various non-drilling activities take place. Records are usually kept of such intervals but that is not always the case. A recorder is needed that places no clerical burdens upon the drilling activity but does record the total time of motor operation. Turbines are used to drive apparatus down hole, including a drill head. Positive displacement motors now operating are usually of the progressing cavity type. Progressing cavity motors have rotors with lobes that progress around the stator which usually has one more cavity than the rotor has lobes. The rotor rotational axis progresses around the stator centerline at a rate that is equal to the rotor rpm times the number of stator cavities. The rotor rotation is in a direction opposite that of the orbital movement. In an eight-cavity stator, a rotor turning clockwise at two hundred rpm has a center line orbiting the stator center line at sixteen hundred times per minute counter clockwise. The diameter of the orbit may be about three-quarters of an inch on a commonly used motor.
Users of down hole drilling motors often require that the rotor be topped by a security flange to aid in recovery in case of disruptive failure of motor or drill string components. The flange atop the rotor places an unusual demand upon any contrivances or instruments connected to the rotor.
Operations down hole involve very high hydrostatic pressures and the temperature commonly approaches three hundred degrees Fahrenheit. Only specialized electric storage batteries can operate at that temperature. Few batteries or instruments can operate at the hydrostatic pressure, and further limitations apply to instruments and batteries. There is a need for a time recorder that does not rely upon batteries and that can be sealed from the pressure.
A housing is connected to the motor rotor shaft, ideally at the top end, to carry a timer. The timer is preferably a chronograph with associated features that at least turn it on and off in coordination with starting and stopping of motor rotation. On progressing cavity motors with rotor shafts with center lines that orbit the motor housing center lines, a horizontal pendulum free to rotate around the rotor axis will tend to remain in a situation with the pendulum mass farthest from the housing center line. As long as the pendulum is allowed to rotate around the rotor axis, and is forced to a deflected state, it can produce torque to power a timer. The torque is used to start and stop the timer in response to starting and stopping of the motor.
The term pendulum is normally associated with a suspended mass that responds to the acceleration of gravity with the mass tending to return to a line that includes its suspension point and is the gravity vector. In this disclosure, the mass is situated to respond to the acceleration vector related to rotation. The point of suspension rotates relative to the acceleration vector produced by rotation. When the mass is displaced from the acceleration vector, it tends to return and can produce torque. The rotation of the suspension point, with the torque, provides power.
The general description assumes a motor with a vertical axis. Drilling motors may be used off vertical, even horizontal. The vertical assumption aids description but is not to be construed as limitation.
The clock winding action can function as a run timer if very little spring energy is stored by a clock spring. Further, if input torque from the pendulum is sufficiently regulated, no clock spring is needed. Run time, then, is simply the elapsed time indicated by the clock. The ordinary clock is set up for twelve hours, then repeats. Motors may run several hundred hours and a clock read out can be geared to produce units, tens, hundreds and thousands of hours.
Alternatively, sufficient power can be stored in a selected clock spring to run one thousand hours and no winding during a common motor run is needed. Starting and stopping the clock in response to motor starting and stopping is then needed. The pendulum, in that case, can be used to perform the clock control function.
The preferred embodiment for a positive displacement motor uses the pendulum for running the time recording function with no need for an energy storing spring. For turbine related timing, centrifugal force responsive elements can turn the timer on and off. The full-run, timer-powering, spring is then preferred, and is usable on the positive displacement motors. The centrifugal switch used herein for clock control can operate if the motor is any degree off vertical.
Starting and stopping of clock work is commonly practiced, mostly on watches. Such controls usually interfere with the escapement mechanism during the stop interval, and the timing starts when the interference is removed. The pendulum can rotate constantly and produce torque to move an element that stops and starts the escapement mechanism. The arrangement would stop the clockwork in the absence of torque produced by the pendulum.
When the motor is to be used in circumstances under which battery powered timers can function, the contrivance used to turn on a timer will operate a switch in the battery power circuit.
It is an object of this invention to provide a timer that will run only when the motor runs, and provide read-out as a total of run time.
It is another object of this invention to provide a run time totalizer that is powered by apparatus that senses the orbital movement of the rotor centerline about the motor housing centerline.
It is yet another object of the invention to provide a spring powered time totalizer that is stopped and started in accordance with the stopping and starting of the motor
These and other objects, advantages, and features of this invention will be apparent to those skilled in the art from a consideration of this specification, including the attached claims and appended claims.